1. Field
Example embodiments relate to oscillators and methods of operating the same.
2. Description of the Related Art
Oscillators are devices that generate signals having a regular cycle and are mainly used in wireless communication systems (e.g., mobile communication terminals, satellite/radar communication devices, wireless network devices, or automobile communication devices), as well as analog sound synthesizers. Mobile communication devices operate in specific frequency bands, and a voltage controlled oscillator (VCO) is used to generate a specific frequency band.
Essential characteristics of an oscillator include a quality factor, output power and phase noise. The higher the quality factor and output power and the lower the phase noise, the better the performance of the oscillator. Recently, because highly efficient and small communication devices are required and an operating frequency band has become high, small size and large output oscillators having a high quality factor and lower phase noise are required.
A spin torque oscillator using a spin transfer torque has been recently introduced. The spin torque oscillator may be classified as a nanopillar structure or a point contact structure. The spin torque oscillator has drawn attention as an advanced oscillator because the spin torque oscillator may be manufactured to be much smaller than general inductor and capacitor (LC) oscillators and general film bulk acoustic resonator (FBAR) oscillators. The spin torque oscillator may have a relatively high quality factor.
However, in a general spin torque oscillator, an angle of change of a magnetic moment (i.e., a spin) is small and thus the output power is low.